The present invention relates to a method of filling a tube system with a rinsing liquid while maintaining sterility, and a tube system for use with this method. In addition, the present invention relates to a safety cap unit for use with the tube system.
When treating various acute and chronic diseases, it may be necessary to perform a treatment of body fluids in an extracorporeal circulation outside the body. Such treatments are performed in hemodialysis or hemofiltration, where blood is subjected to a dialysis treatment in a dialyzer. In addition to hemodialysis or hemofiltration equipment, cell separators are also known which make it possible to separate blood of a patient into fractions. Cell separation is also performed in an extracorporeal circulation.
Since the blood treatment must be performed under sterile conditions, tube systems which are intended for a single use typically are used with current blood treatment or processing equipment. For connection to the patient, the single-use tube systems have a blood inlet line with an arterial patient connection and a blood return line with a venous patient connection.
To prepare an extracorporeal circulation, the part of the tube system intended for blood typically is rinsed with a physiological saline solution and is filled so as to admit as little air as possible by using either a non-recirculating or recirculating method of filling.
With non-recirculating methods of filling the tube system, the saline solution is drawn from a container through the blood inlet line, and then the rinsing liquid flows through the tube system and is sent through the blood return line into another container which serves to hold the used saline solution. This method has the disadvantage of a relatively high consumption of rinsing liquid.
Recirculating methods, where the supply container and the collecting container are combined, differ from the non-recirculating methods of filling the tube system. In this way, the saline solution can circulate through the tube system repeatedly without having to refill the container. For connecting the patient connections, the container has connection parts with self-sealing septa which are punctured by the cannulas of the patient connections. The advantage of the recirculating methods is the low consumption of rinsing liquid. However, they have the disadvantage that when connecting the patient connections to the container, there is the risk that the cannulas of the patient connections might be damaged. Optimally, these cannulas should be ground and sharp for puncturing the containers of the patient. European Patent Application No. 203,513 A, for example, discloses a medical bag arrangement for recirculation of the rinsing liquid.
European Patent Application No. 305,364 A describes a method of filling a tube system where the patient connections are short-circuited by a bridge, with the saline solution being supplied through a side branch of the tube system. The patient connections can be introduced into the short-circuit piece at the factory, so that the tube system is available to the user in a sterile condition. One disadvantage is that the rinsing liquid recirculates through the patient connections. This leads to a high flow resistance, especially with so-called closed systems in which the needle adapters are fixedly attached to the cannulas. Since the two patient connections are interconnected by the short-circuit piece, there is the risk, especially with complicated tube systems such as those conventionally used in cell separation, that one of the patient connections might become detached from the short-circuit piece when inserting the tube system, thus violating the sterility requirement. Another disadvantage is that one patient connection is already being exposed to an unsterile environment when the other connection is being removed from the short-circuit piece. Therefore, the tube connection must be connected to the patient very quickly.
There are also extracorporeal tube systems with regional anticoagulation. This is understood to include systems in which blood is treated with anticoagulant not inside the patient but instead only within the extracorporeal circulation. This is usually accomplished with a sodium citrate solution which is added to the blood downstream from the patient connection on the suction side. Such systems generally have a so-called xe2x80x9ckeep vein openxe2x80x9d function which makes it possible to rinse the coagulable blood out of the cannulas and back into the patient in the event of a machine shutdown, thereby preventing coagulation inside the cannulas. Tube systems having a keep vein open function typically have rinsing liquid lines which open into the blood inlet and return lines in the immediate vicinity of the patient connections. In the case of a machine shutdown, the saline solution is supplied from a bag to the tube system through the rinsing liquid lines.
An object of the present invention is to provide a method that permits filling of a tube system, even those with regional anticoagulation, while maintaining sterility without increasing the flow resistance or exposing one of the patient connections to an unsterile environment when the other connection is ready for connection to the patient.
The present invention provides a method of filling a tube system with a rinsing liquid while maintaining the sterility of the tube system, comprising a blood inlet line with an arterial patient connection and a blood return line with a venous patient connection, where a rinsing liquid inlet line branches off from the blood inlet line downstream from the arterial patient connection, and a rinsing liquid return line branches off from the blood return line upstream from the venous patient connection. The method is characterized in that rinsing liquid is conveyed from a rinsing liquid container back into the rinsing liquid inlet line, establishing a liquid connection between the rinsing liquid inlet and return lines, with the venous patient connection being sealed liquid-tight with a venous safety cap and the arterial patient connection being sealed liquid-tight with an arterial safety cap which can be removed from the patient connections in order to connect the tube system.
The present invention also provides a tube system for use with the present method, with a blood inlet line (5) having an arterial patient connection (1) which is sealed liquid-tight with an arterial safety cap (2) which can be removed from the patient connection for connecting the tube system. A blood return line (15) has a venous patient connection (3) which is sealed liquid-tight with a venous safety cap (4) that can be removed from the patient connection for connecting the tube system. A rinsing liquid inlet line (21) branches off from the blood inlet line downstream from the arterial patient connection, and a rinsing liquid return line (25) branches off from the blood return line upstream from the venous patient connection, with the rinsing liquid inlet line and the rinsing liquid return line being connected to a rinsing liquid container (20) that accommodates the rinsing liquid. A first cut-off device (30) is connected to the rinsing liquid inlet line downstream from the rinsing liquid container, and a second cut-off device (32) is connected to the rinsing liquid return line upstream from the rinsing liquid container. The tube system is characterized in that a short-circuit line (35) connecting the rinsing liquid inlet line (21) and rinsing liquid return line (25) is provided, with a third cut-off device (36) or a pressure control valve (51) being connected to this line.
The present invention further provides a safety cap unit for a tube system for use with the present method with an interior venous and arterial chamber (42, 43) for accommodating the venous and arterial patient connections (1, 3) of the tube system under sterile conditions, and with the interior venous chamber (43) being connected to the environment by a hydrophobic membrane (47).
With the method according to the present invention, the rinsing liquid is recirculated not through the patient connections but through the rinsing liquid lines. The rinsing liquid flows from a rinsing liquid container through the rinsing liquid inlet line, the blood inlet line, the blood return line and the rinsing liquid return line and then goes back to the rinsing liquid inlet line. Even if the safety cap becomes detached from one of the patient connections, the other patient connection is still exposed to a sterile environment.
This method can be implemented in many variants and combinations which are made possible by different tube systems. The main points of the modifications are the safety caps on the patient connections and the line configuration of the tube system in the vicinity of the rinsing liquid containers.
The term xe2x80x9cpatient connectionxe2x80x9d is understood below to refer to all means making it possible to connect the tube system to the blood vessels of the patient. The patient connections may be designed as needle adapters for attaching cannulas, but the cannulas may also be already attached to the needle adapters or they may be designed in one piece with the connections. Safety caps are hereinafter understood to refer to all devices enclosing the patient connection under sterile conditions.
In order for the safety caps to be filled completely with rinsing liquid during the rinsing operation, air in the line section of the blood inlet or return line upstream or downstream from the branch in the rinsing liquid inlet or return line is preferably let out of the safety caps. For this purpose, the safety caps have hydrophobic membranes that prevent the passage of liquid but allow air to escape.
The venous and arterial safety caps may be designed as separate parts, but it is also possible for the two safety caps to form one unit. If the venous and arterial safety caps are designed in one piece, the interior chambers of the safety caps can be vented independently of one another, but it is also possible for the air in the venous safety cap to be transferred to the arterial safety cap.
The safety cap unit for a tube system for use with the one variant of the method according to the present invention has an interior venous chamber and an interior arterial chamber to accommodate the sterile venous and arterial patient connections, respectively, where at least the interior venous chamber is connected to the environment through a hydrophobic membrane, while the safety cap unit for a tube system for use with the other variant of the method according to the present invention has two interior chambers connected to one another by a hydrophobic membrane.